Question

Two elements $X$ (atomic mass $=75)$ and $Y$ (atomic mass $=16)$ combine to give a compound having $75.8\%$ of $X$. The formula of the compound is

• A. $XY$
• B. $X_{2}Y$
• C. $X_2{Y}_2$
• D. $X_2{Y}_3$

Answer 1

Answer: (D)

$X_2{Y}_3$

100 g of compound will contain 75.8 g of $X$ and $100-75.8=24.2$ g of $Y$

The number of moles of $X$ $=\frac{\text{75.8 g}}{\text{75}}=\text{1.01 mol}$

The number of moles of $Y$ $=\frac{\text{24.2 g}}{\text{16}}=\text{1.51 mol}$

The mole ratio $X:Y$ $=1.01:1.51=2:3$

The formula of the compound is: $X_2{Y}_3$.